What Happened To Us?
by EFstrawberryjam
Summary: After the guys accept to watch one of Donnie's 'ground breaking' mutagen experiments, the vile explodes causing the mutagen to burst out over the four turtles. Little do they know that this little experiment was going to change their life's forever. Rated T for violence and Raph's mouth.
1. Prologue

**Just to let you know I don't own TMNT. This is my first Fanfiction so I hope you enjoy. I'm not really sure how this is going to go, so make sure to review to let me know if I should continue! what you liked/disliked, what I could improve, etc. Thanks.**

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(Leo's POV)

I take a deep breath trying to sink deeper into my meditation. After everything that has happened...happened to us...how could we look at each other the same way. I break out of my meditation and walk out of the dojo looking for anyone I could talk to. Nobody was around, although I could still hear the mad growls coming from Raph's room. He hadn't come out of his room since the...incident. He didn't want to, too afraid of what he had done and what he might do to us. I assumed Donnie was in the lab still desperately trying to figure out exactly what had happened. As for Mikey, I wasn't sure, he'd seemed so different since...since the incident and was out much more often, almost as if he was trying to get away for us.

I began walking towards Raph's room before hesitating and turning to the lab. I'd go check on Donnie first. Opening the door I saw the purple masked head of the turtle resting on his messy desk, pencils and papers sitting in stacks around him. I smiled taking the pencil from his hand and placing it in his ever growing cup of pencils. I looked around shuddering as I see a small patch of the stuff that brought up all of this, the mutagen. How did something so small become so big? What happened to us?

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 **Ohhh, cliffhangers. Thanks for reading the prologue to 'What Happened To Us?'.**


	2. Chapter 1: The Wrong Ingredient

I don't own TMNT, just a warning.

Just before the chapter begins wanna shout out to some of my friends and Empoleonmaster23 for helping me with ideas with this story. Also thanks to Szary Wilk for being the first to follow the production of this story. Enjoy.

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(Raph's POV)

"Guys, guys, I need to show you something! You won't believe what I've discovered!" Donnie ran into the room his eyes lit up with excitement over his 'amazing' discovery.

"Yeah sure Sherlock, what is it?" My eyes gazed aggressively off my punching bag and towards Donnie, almost as if he was next.

"Just come on I want you to witness as I make history, where's Leo?"

"In the dojo, like usual, I mean where else would he be?!"

I walk into the lab and scowl as I see Mikey spinning around upside down on Donnie's lab chair,

"What are you doing Mikey?"

He giggles throwing his arms towards the ground to catch himself before he falls,

"The world looks so different from outside down Raphie, you should try it one day,"

I sigh trying to ignore the fact he called me 'Raphie',"You're such an idiot sometimes, now can you tell me what the shell Donnie's so excited about?"

"I don't know something to do with mutagen...I think"

Raising my eyebrow I sit down "Isn't that kind of dangerous?"

"Donnie says it's fine, nothing over the top"

Keeping my eyes fixed onto Mikey until Donnie and Leo enter, I sigh "Finally, now what is the 'amazing' discovery Donnie" I say making obvious quotation marks on the word 'amazing'.

"You'll see" I stare at my direct younger brother as he grabs a vile full of what I believe is this new type of mutagen, "Now, look at this" He takes an eye dropper and picks up some of the liquid "What I think I've discovered is quite extraordinary, it can change the way we live! It'll hopefully make us...well...more human!"

"What?!" Mikey's head spins around so fast it almost comes of its hinges "Really! Then we can go out in day and no-one while judge us and we can also—"

"Well it has to work first!" I yell, shutting my younger brother up with my anger tone.

As if that was a cue, Donnie elegantly drops a single drop of the mutagen mix into the normal mutagen and it begins to bubble. Mikey jumps up from the swivel chair he was on, his eyes as large as saucers, when suddenly the two liquids start bubbling more violently and the beaker begins to fill up rapidly.

"Uhh Donnie is that supposed to—"

"GET DOWN!"

Everyone jumps to get on the ground, when suddenly the vulgar, now light blue mutagen mix before them explodes everywhere, including spilling onto the 4 terrapins. Leonardo, upon seeing the substance, swiftly grabs the closest piece of clean cloth and begins wiping the liquid off his cheek.

"ARE YOU SURE YOU KNOW WHAT YOU'RE FUC-"

"Raphael," Leo interrupts before I can finish, "That is quite enough." He takes the cloth from my hand and passes it to Donnie.

"I d-don't know w-what happened!" Donnie stuttered, blushing viciously as he wipes the substance off his neck.

Leo sighs, obviously a little annoyed and swiftly turns and walks out of the room.

"Wait Leo...it wasn't supposed to do that, something must've been wrong" Donnie sighs as he takes the cloth of Mikey as chucks it in the bin, "Something must've been wrong, maybe an ingredient in the mutagen mix's-"

As Donnie continues on with his sciency babble, I look over at Mikey as he whispers something so faint that it's almost impossible to hear.

"Uhhhh, guys?" Mikey points towards the door where Leo had just been "Did anyone else notice that Leo's cheek is glowing light blue?"

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(10 minutes later)

(Leo's POV)

I can't believe I had just left! I was supposed to be the leader, I can't just let my anger consume me like that! I have to go apology. No, it was Donnie's fault, but he's my little brother, he obviously didn't mean it. Why is being leader so hard! No I have to go say sorry for my aggressive actions.

I get up out of the lotus position I'm sitting in and make my way towards the dojo door. Why does my cheek hurt so much, I haven't hurt it have I? I make my way to the bathroom and stare into the mirror. What the?! Why is my cheek glowing...blue? I touch it and hiss slightly at the sharp jab of pain that radiates of it. Is this from that mutagen mix, what did it do?

I go to leave the bathroom when my cheek suddenly flares up and I fall over coughing.

"I don't feel so well..." is all I can can say as I black out.

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(Mikey's POV)

I race after Leo, something was definitely wrong. My first instinct is to look in the dojo, but he isn't there. Then when I hear it, something I never want to hear from any of my brothers, I hear Leo coughing. This isn't the average cough though, this the type that you hear someone doing when they're choking for breath. I race towards the sound, ending up in the bathroom. He's on the floor and looks unconscious.

"Leo..?" I ask poking him. "Leo!" He doesn't answer and I begin to fret. "Uhh no, I need to get the guys" I mumble, but as I feel something pull me back.

"I don't think your going anyway Michelangelo"

"Leo...?"

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(Leo's POV)

I'm submerged into darkness and feel the restraints my soul has on my body begin to unweave. My head is pounding and I'm beginning to feel lightheaded. What's going on? What's happening to me?

A piercing pain suddenly comes from my cheek and I hiss putting my hand over it. "Not again, what was in that mixture because my body certainly did not like it! I feel myself be completely submerged into my soul and step down onto the endless void. I never come here unless I'm extremely hurt, why am I here? I walk around a bit until I feel the pain in my cheek suddenly subside. I feel my soul begin to weave again with my body when I get knocked back by something.

Looking up from where i was just standing I stare at myself?!

"Well hello Leonardo, how are you today?"

Shocked by the sight in front of me I manage to mumble out a couple of words, "Who are you?"

"Why is it that hard to tell," he says staring down at the unsheathed katanas in his hands "I thought you'd know what you looked like by now..."

Before I could answer he lunges forwards at me, pushing his foot down onto my plastron.

"Do you submit?" He states beginning to push harder on my plastron "You'll be cutting it close if you don't" He presses his katana lightly onto my arm on the word 'cutting' drawing blood

I grunt trying to move from his grip, but I can't "What do you want?"

"Control"

He smacks the butt of his katana into my head and before I cannot do anything all I see is black.

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Ok, that was pretty wild wasn't it. I wonder what Evil Leo wants with the guys? Does it have anything to do with this mutagen mix? We'll have to find out next time, won't we? Anyway thanks for reading, feel free to comment or review as it would be greatly appreciated.


	3. Chapter 2: The Beginning

Welcome back to another chapter of 'What Happened To Us?'. Sorry it's been a while, but just a quick reminder, I don't own TMNT, also thanks to everyone who has been reading! WARNING: Swearing below, reading with caution if that offends you.

For every evil under the sun

There is a remedy or there is none.

If there be one, seek till you find it;

If there be none, never mind it.

\- Mother Goose Rhymes

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(Donnie's POV)

I sprint out of the lab as I hear Mikey scream. I see Raph running over to the source of the noise as well, and wonder if Leo is already there. I begin to wonder what it is, probably nothing too bad, this is Mikey we're talking about so it could be anything.

Before I can get to the door of Leo's room though (the source of the noise) it flings open and Mikey runs into me.

"Move dude, we need to get out of here!"

"What is it shell brain?" Raph glares and Mikey, tapping his foot on the ground with impatience.

"Well it's-"

"Why hello brothers, I have just having some fun with dear Michelangelo here" a sickly low version of Leo's voice interrupts.

"Leo, what the shell is wrong with your voice, what did Mikey do?"

"Dear dear Raphael, Michelangelo here did absolutely nothing," Leo chuckles quietly "You could just say I embraced my darker side"

He walks out of the darkness of his room, unsheathing his katanas in the process, his eyes are a much darker blue than usual and have a tint of black in them, his skin is a darker green, almost grey and his shell holds an dark grey ambience to it. His mask is tattered and looks as if there is blood down the side of it, it's terrifying. All I can do is stare as his jumps towards Raph and slices the blade down his arm.

"Arghh, Leo what the shell! What was that for?!"

"That's not Leo!" Mikey grabs his nunchucks and blocks Leo's attack towards him

"Then who is it!" I duck as Leo katana slices right through where I was seconds ago.

"I don't know, that's just not Leo!"

"You'll know very soon, so there's no reason to guess," Leo smiled "Now you three should leave before I finish you off myself, after all I always better without you"

Raph growls, but stands his ground in front of us, everyone knows how he hates that Leo is better at certain things over him, but Leo never points it out, and what's with his appearance?

Leo goes to once again attack us for not leaving, but before he can reach Raph once more he suddenly breaks down coughing onto the floor.

"Guys...?" Leo splutters as his breathing begins to steady out. "You need to go...something is very wrong, the…the mixtu-" he collapses, coughing even more

"Leo, what ta fuck happened bro? What's going on?"

"You just need to...I can't keep control for much longer" he stumbles, kneeling over once more, holding his head and coughing wildly.

I go to help him out, but Raph holds me back.

"Donnie, as much as I hate to admit it, Leo's the leader and we have to listen to his orders, now come on"

He pulls Mikey and I away down to the lab, locking the door I turn around to face Raph and Mikey. "That should hold him if he comes for us, now we should get you two cleaned up"

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(Raph's POV)

I sit down next to Mikey on a cot as Donnie scavengers through some cupboards for the right medical supplies.

"How do you feel Raph?" Mikey baby blue eyes are wide and staring over at me with intent.

"I'm fine…what's wrong with Leo, Don?" He turns around chucking a bandage to me and taking some papers from his desk.

"I don't know, but he was about to say something else, that's probably what it is"

"Maybe it had something to do with his glowing cheek" Mikey points to his cheek, making blinking signals with his hand.

"But, why would it be glowing? That makes no sense" Donnie shoves his hand into his hands and sighs loudly "I just don't understand, this is all my fault isn't it?!"

"No Don, it's not, we have no idea what the thing is making Leo go all crazy, so how would it be your fault bro?" Mikey coos.

"It doesn't matter who's fault it is now, we need to figure out how to fix it"

"What was he trying to tell us?" Don sighs once more, sitting down in his lab chair. "It could've been anything!"

"Something about mist, I think"

"No he said mix, as in mixture maybe."

"Hmmmmm, what about the one that made Leo glow, the blue one"

"It would make sense I suppose, it's the only thing in the last couple of days that has seemed to affect him"

"Where is he now, I'm afraid we're going to need a blood sample for this experiment"

"I'll get him" I push myself up from the cot and make my way to the door

"Watch out Raph, he could still be dangerous"

"Yeah yeah, whatever"

I walk outside of the lab getting into a mild defensive stance as I make my way towards the area he was in a couple of minutes ago. Before I can control it, my brain starts thinking into overdrive as I walk. What did he mean 'after all I always better without you', would Leo really think that about us? No of course not, he was after all being controlled or some shit like that.

Before I can go any further, Donnie's voice interrupts my thoughts

"Uhh Raph I think we have a problem!"

I run back into the room to see Donnie sitting in front of Mikey, who is staring at the ground and laughing?

"What's going on?"

"I don't know, he was just sitting here and then he started coughing and groaning, before he just started laughing like a crazy person"

"Like…like…oh no, Donnie I think the thing that is happening to Leo is now happening to Mikey, we need to do something"

"What can we do! I have no idea what's going on Raph! What if it happens to us?!"

"I won't let that happen!"

* * *

So what's going on with the family I wonder, surprised that it's not obvious to the guys, but they do have pretty busy lives. :P

Anyway thanks for reading the chapter. I'm going away to a place without in internet over the next two weeks, but I need some help in the meantime:

-Do you want any other new characters to be implemented (April, Splinter, etc.)

-Do you want the mixture to affect only one turtle at a time or more than one?

I promise I'll keep writing on my 'vacation'. See ya soon.


	4. Chapter 3: Feeling The Effects: P1

**So I'm back, cool.**

 **I don't own TMNT, because if I did this would exist as an episode, so it's probably a good thing I don't. Thanks to everyone who's been reading, as long as you're happy reading it, I'm happy writing it!**

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(Leo's POV)

(Inside the astral plain)

"Stay away from me and all my family!"

"But why would _we_ do that Leonardo, your energy is just so _fun_ to control"

"How did you even come to exist faker, and how did you get inside of me?"

"Haha, so many questions Leonardo, haven't you learnt that curiously killed the cat, or better yet turtle" my faker begins to circle me, holding out his katanas towards my plastron. "But, if you must know, I came to exist because of an experiment"

"Who's experiment? Who sent you akuma?!" I get into a defensive stance and go to draw my katanas from their holders, when I realise they're not there.

"Whoops, looks like someone forgot their weapons, where did you leave those?"

I growl and hold my fists up in a boxing stance.

"Hmm, fighting with our fists are we then, I'll play along" He throws his katanas across the ground and they disappear into nothingness.

We then proceed to circle each other until he makes the first move, "You wanna know where I came from Leonardo?"

I glare, but don't interrupt as he continues.

"Do you remember that mutagen mixture Donatello showed you about—" He checks his non-existence watch, "20 minutes ago? Let's just say _we_ were the wrong ingredient"

"We?"

He smirks and shoves into me, "Yes, we, as in us"

"You and who?"

"Me and _my_ brothers"

"What are their names?"

"Why they are the same as yours. Do you know your brothers names?"

"DON'T YOU DARE TOUCH MY BROTHERS" I lunge at him, throwing some kicks and punches

"I won't, but I won't promise anything from _my_ brothers, they want control as well, but I hardly believe that they'll get it, considering I'm so much better than all of them combined" he smirks again, and blocks my attacks, "Let me rephrase that, we are so much better than all of them combine Leonardo, join me, we can rule together"

"I would never betray my brothers, I would never be that selfish!"

"That's not what your brothers see, not while I'm in control! I'll twist their views on you, you shall betray them, you shall obey me!"

"NOT FOR LONG SUCKER"

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(Mikey's POV)

I feel suddenly lightheaded, even though I'm just sitting with D in the lab. Raph has just gone to try and 'help' Leo back here to get a blood sample, at least that's what he said, but I hardly believe it. I close my eyes thinking back to the events over the last 20 minutes, what happened to Leo? He looked greyer than he should be and was angry at me for no reason, well angrier than usual. As I reopen my eyes I find myself in the astral plain. 'What, how did I get here?'

"Heeellloooo?"

"Hehehe, hello"

"Oh hi, can you help m—wait, who are you?"

"Why I'm just uhhh your self conscious, yeah that!"

"Oh, ok, can you help me?"

"With what Michelangelo?"

"I got stuck he—wait who do you know my name?!"

"I'm your self conscious, remember?" He walks into the long hot revealing his steel grey skin and dark grey shell and plastron. He holds my signature nunchucks in his belt and has an orange mask that looks as if it's been kicked through the dirt. His eyes are a much darker blue almost like Leo's.

"But, you don't look like me," I cock my head to the side and examine his steel grey skin "You look greyer than me, kinder like Leo was..."

My doppelgänger frowns and takes his nunchucks from his belt "You are smarter than you look, but lucky I like a good fight!"

He charges at me, I try to dodge, but he catches my leg and throws my across the ground. I grunt and pick myself up, reaching for my own nunchucks until I realise they're not there.

"Yeah sorry _buddy,_ victims don't get their weapons here"

"Who said I was the victim, huh?" I lunge at him, sweeping his legs beneath him.

"Oh, is this how we're gonna do it now?" He laughs as he releases his kusirigama blade from inside of his right nun-chuck and swings it at my arm, only missing by inches.

"Woah, personal space dude" I say backflipping away and running a random direction away from him. 'If I can't get close to him, how am I going to fight him. I need a different strategie, but this would do for now.'

"Uhh, chicken are you?" He races after me, clucking like a chicken.

"Cheater…"

After running for what feels like over an hour I turn around to check if he's still following. He's nowhere insight, so this is what gives me the chance to get a well-deserved—wait what's that fighting sound?

I spin my head around and walk towards a dark patch in the astral plane which seems to be producing fighting sounds? Stepping through what seems to be a dark wall, I almost fall straight to my death, my ninja instincts only just holding me back.

"Woah, where am I?"

" _Join me, we can rule together_ "

I stare down upon the scene infront of me. Leo seems to be fighting with a greyer, darker version of himself.

" _I would never betray my brothers, I would never be that selfish!_ "

'Yeah Leo, you fight him, we believe in you!' I think as I look for any way down to help him.

" _That's not what your brothers see, not while I'm in control! I'll twist their views on you, you shall betray them, you shall obey me!"_

'Well here goes nothing' I jump down aiming for the dark Leo and tackle him to the ground "NOT FOR LONG SUCKER!"

"Mikey?! What are you doing here?!"

"Umm, you know, HELPING! Figured you needed it," I roll my eyes as I continue my wrestling match with dark Leo "Now get out of here, I can handle this"

"No I'm not going to—"

"Well, well, well Michelangelo, don't interrupt others fights, it's very rude" my darker version jumps down, giggling menacingly, all the while slyly producing his weapons from his belt "Besides, it wouldn't be very fair would it?"

"Crap," I mumble staring around dark Leo to glare at my darker version "We got company," 'Maybe I do need a little help' "Uhh Leo?"

"Yes Mikey"

"Can you umm, please take care of dark me here", I point to my darker self and he nods.

"Yeah, will do" He say roundhouse as kicks the darker version of himself into the void and goes to tackle the dark version of me as he comes towards me.

"You shall not decide own names, we are Dākureonarudo and Kurai Mikeranjero, and you shall not call us anything else!"

I frown at the obviously uncreative names" Wow who named you cause they're terrible." I smile over to Leo as he looks over towards me. "Now let's get these two morons outta here bro!"

(A couple of fighting minutes later)

I see Kurai Mike dude go flying past me and go to finish Dākureon off when he catches my kick.

"Tsk tsk tsk Michelangelo, just a tad too slow for me," he smirks before twisting my leg around and kicking me into the ground "Though you were the faster, didn't you?"

I go to shake myself off, but Dākureon sticks his foot into my plastron, holding me down.

"Look at how easy this was Leonardo, this is what we can do, join me"

"I would never"

"Than I shall kill him"

"DON'T YOU DARE YOU—"

"Leo, you need to go" I look up at him, grimacing as Dākureon pushing down harder on my plastron.

"Mikey I can't"

"I can handle things here," I squirm to try and get out of Dākureon's grip, but it's too strong "Go warn the others"

"I-I" He looks down at me, we both know that I'll lose, but he knows that he should go warn the others at the same time. "I'm sorry"

"I'll see you soon"

And with that Leo runs off in the opposite direction to 'wake up' and warn the others, all the while I'm left with these two.

"Whatcha wanna do with em boss?" Kurai Mike giggles

"You can have him"

"Finally"

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 **Just some notes: So...just in case you were wondering, this is a Part 1 because when I was writing this chapter it became too long, so I wanted to split it up into at least two parts to have equal(ish) chapters. Also the reason Mikey's part is so long is because I feel he hasn't really had a big POV yet. Donnie will get one next chapter (I think). Please don't search up the dark versions of the turtles name's as I don't wanna be exposed.**

 **Thank-you to everyone, who has the patience to return to read this monstrosity, it's greatly appreciated. See ya soon**


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